Abstract
This study investigates the impact of different surfactants and dispersion techniques on the friction and wear behavior of WS2 and MoS2 nanoparticles additives in a Polyalphaolefin (PAO) base oil under boundary lubrication conditions. The nanoparticles were dispersed using Oleic acid (OA) and Polyvinylpyrrolidone (PVP) to investigate their impact on particle agglomeration. The size distribution of the dispersed nanoparticles in PAO was measured by dynamic light scattering. The nanoparticles treated using PVP resulted in the most stable particle size. Friction studies showed that nanoparticle agglomeration reduction and the homogeneity of the suspension did not significantly impact the friction reduction behavior of the lubricant. Reciprocating wear experiments showed that, for our test conditions, both WS2 and MoS2 nano additives exhibited maximum wear depth reduction (45%) when using the PVP surface treatment compared to base oil. The wear results confirmed the significance of minimizing agglomeration and promoting high dispersion in promoting favorable wear resistance under boundary lubricant conditions. Analysis of the wear surfaces showed that a tribofilm formation was the primary wear reduction mechanism for WS2 particles treated by PVP while, in the case of MoS2 treated by PVP, the mechanism was load sharing via particles rolling and/or sliding at the interface.
Highlights
Several studies have shown that tribological behavior of a lubricant can be improved by dispersing a small amount of nanomaterials in base oil
We describe the results related to reducing agglomeration of nanoparticle additives when dispersed in base oil
Results related to reducing agglomeration of nanoparticle additives when dispersed in base oil
Summary
Several studies have shown that tribological behavior of a lubricant can be improved by dispersing a small amount of nanomaterials in base oil. The literature shows that dispersion of nanoparticles additives can be improved by using a number of techniques including sonicating, which includes both bath or probe sonication, adding a surfactant, or a combination of the previously mentioned techniques [3,4,5,6,7,8,9,10,11]. We selected two dichalcogenides nanoparticles known as WS2 and MoS2 that have been shown to improve tribological behavior as additives. Other studies investigated the dispersion of the MoS2 nanoparticles and showed that the agglomeration could be reduced by adding surfactant via bath sonication [21,22,23]. There are studies that have demonstrated improved tribological behavior using WS2 nanoparticle additives with Refs. There are studies that have demonstrated improved tribological behavior using WS2 nanoparticle additives with Refs. [16,24,25,26,27,28,29,30]
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